1. Field of the Invention
The present invention relates to an image transfer apparatus by which the superimposed sheets in which an image receiving sheet on which an image is formed by a thermal heat-transfer printer, or a laser thermal transfer printer (other than them, any one of printers which can print on the transfer sheet, such as an inkjet printer, may be allowable), and the transfer sheet onto which an image is to be transferred, are superimposed, are passed between the heat roller pair, and an image formed on the image receiving sheet is transferred onto the transfer sheet.
2. Description of the Related Art
When a print plate is made from a color document, and a print of a large number of sheets is conducted, a proof print is conducted and after the finishing is confirmed, then an actual print is conducted. In this case, in a proof print process, a color proof is made and confirmed. Such the color proof is obtained such that, after an image is formed on the image receiving sheet by a thermal printer, an image formed on the image receiving sheet is transferred onto the transfer sheet by an image transfer apparatus.
FIG. 8 shows a conventional general image transfer apparatus. In the same drawing, numeral 1 is an image transfer apparatus, and in this image transfer apparatus, heat rollers 41 and 42 are respectively provided by each one lower and upper being opposed to each other, and on its downstream, nip rollers 51 and 52 are respectively provided upper and lower being opposed to each other. A heat cover 4 covers the periphery of the heat rollers 41 and 42, and prevents the heat dissipation of the heat rollers 41 and 42, and a protective transfer cover 5 further covers its outside including the nip rollers 51 and 52. Further, on the entry side of the image transfer apparatus 1, an insertion platform 2 is provided, and on the one hand, on its delivery side, a delivery base 3 is provided. The heat rollers 41 and 42 are made of, for example, aluminum material, and its outer peripheral surface is covered by a cover layer formed of lubber, and heaters are internally provided at the center of heat rollers 41 and 42. In the heat rollers 41 and 42 provided upper and lower being opposed to each other, one (for example, the lower roller) is for driving, and the other roller (the upper roller) is a driven one. The superimposed sheet of the transfer sheet and the image receiving sheet is passed between the upper and lower heat rollers 41 and 42 while being heated and pressed, and the image on the image receiving sheet is transferred onto the transfer sheet, and after that, an image receiving sheet supporting body is peeled from the transfer sheet by the hand, and the image is obtained on the transfer sheet.
FIG. 9 is a view for explaining in detail the shape of heat roller pair 41 and 42 in FIG. 8, and the heat roller 41 is a driving roller of a straight type of the roller length of 400 mm (that is, a cylindrical type in which all of the diameters of the both ends of heat roller xcfx861L, xcfx861R and the diameter xcfx861C of the central portion are equal, (for example, 35.8 mm)), and the heat roller 42 is a crown type of driven roller of the roller length of 400 mm (that is, a barrel-shape type in which the diameter xcfx862C of the central portion is a little larger (for example, 36.1 mm) than the diameters xcfx862L, and xcfx862R (for example, 35.8 mm)), and both of heat rollers 41 and 42 are covered by a silicon rubber material of the hardness 60xc2x0 (JIS hardness A).
Onto both sides of the upper side heat roller 42, as the pressing force P, the force of 200xc2x140 N is applied per one side.
Because each of heat roller pair 41 and 42 is supported only at 2 portions of both ends, even when the central portion is deflected a little, by the structure of the combination of the straight-crown types as described above, the uniform pressing force can be obtained at any portion of heat roller pair 41 and 42.
Conventionally, the image transferring is conducted by using such the image transfer apparatus 1 by following 2 methods.
1) One of them is, as shown in FIG. 10, a method in which the image receiving sheet R is superimposed on the transfer sheet P, and the superimposed sheet is passed as it is between the heat roller pair 41 and 42, and the image of the image receiving sheet R is transferred onto the transfer sheet P. That is, in FIG. 10, when the superimposed sheet of the transfer sheet P and the image receiving sheet R which is superimposed on the transfer sheet P, is passed between the upper and lower heat rollers 41 and 42, the superimposed sheet is passed while being heated and pressed, and the image of the image receiving sheet R is transferred onto the transfer sheet P, then, conveyed by the nip rollers 51 and 52, and delivered from the delivery base 3.
In this connection, in this case, when the sheets are passed, the image receiving sheet or the transfer sheet is bent, and the convex and concave wrinkle (hereinafter, called an [indent])is generated. It is considered that its cause is due to the difference of the elongation and shrinkage coming from the difference of material between the transfer sheet P and the image receiving sheet R, or the difference of the thermal expansion rate or humidity absorption rate.
2) In order to solve such the problem, as another method, the present applicant developed a method to use an image transfer apparatus carrier. FIG. 11 shows a transfer method to use the image transfer apparatus carrier.
In FIG. 11, numeral 9 is an image transfer apparatus carrier, and it is structured by a carrier base plate 91 made of a 0.3 mm thick aluminum material, a cover sheet 92 formed of a 0.2 mm thick polyimide material, which covers only the vicinity of the leading edge of the carrier base plate 91 in the advancing direction, and a heat resistive tape 93 to fix the cover sheet 92 to the carrier base plate 91.
In this connection, when the image transfer apparatus carrier 9 is used, initially, the cover sheet 92 is opened, and the superimposed transfer sheet P1 and the image receiving sheet R are inserted between the cover sheet 92 and the carrier base plate 91, and the cover sheet 92 is turned to the original position, and the image receiving sheet and the transfer sheet are nipped from the front and rear surface sides, and the heat resistive tape 93 side is made the leading edge, and the sheets are passed between the heat roller pair 41 and 42.
In this manner, when the image transfer apparatus carrier is used, the transfer sheet P and the image receiving sheet R are nipped between the carrier base plate 91 and the cover sheet 92, and are passed between the heat rollers 41 and 42 while being held by the image transfer carrier 9, thereby, the indent is not generated.
However, the indent is not generated when the image transfer apparatus carrier 9 is used as described above, but, because the heat is absorbed in the aluminum plate, the transmission of the heat becomes undesirable, accordingly, it is necessary that the sheet passing speed is lowered to about {fraction (1/10 )} of the conventional speed, or because it is necessary that the temperature of the heat roller is set higher than the original temperature, the amount of use of the electric power is increased, and it is necessary that the heat resistive temperature of the members is increased, like that the heat resistive structure becomes a large scale. Further, because the image transfer apparatus carrier 9 is ordinary made of an aluminum material, the conveyance path can not be bent, resulting in the hindrance of downsizing of the overall apparatus.
Accordingly, the present applicant developed previously an image transfer method and an image transfer apparatus thereof in which the image transfer apparatus carrier is not used, and the indent is not generated, and the sheet passing speed is the ordinary one, and the amount of use of the electric power can be realized in the ordinary one, and applied for a patent as U.S. patent application Ser. No. 09/639,161.
According to it, in the image transfer apparatus in which the image receiving sheet on which the image is formed and the transfer sheet onto which the image is to be transferred, are superimposed, and passed from the insertion platform between the heat roller pair, and the image formed on the image receiving sheet is transferred onto the transfer sheet, initially, the image receiving sheet is positioned on the insertion platform, and the transfer sheet is superimposed on it, and these sheets are inserted between the heat roller pair in the superimposed condition.
By using FIG. 12 and FIG. 13, the image transfer method according to the preceding invention will be briefly described below. FIG. 12 is a partial sectional perspective view of the image transfer apparatus according to the preceding invention, and FIG. 13 is a view for explaining the image transfer using the image transfer apparatus in FIG. 12.
In FIG. 12, numeral 1 is the image transfer apparatus, and is structured by heat roller pair 41 and 42, a heat cover 4 to cover it, nip roller pair 51 and 52, a protection cover 5 to cover the heat cover 4 and the nip roller pair 51 and 52, an insertion platform 2, and a delivery base 3. Further, another nip roller pair is provided on the outside of the heat cover 4 on the upstream of the heat roller pair 41 and 42, thereby, the superimposed sheet of the image receiving sheet and the transfer sheet can also be securely nipped. Further, the nip roller pair 51 and 52 may also be neglected.
In FIG. 13, a sign R on the insertion platform 2 of the image transfer apparatus 1 is the image receiving sheet on which the image is formed, and a sign P superimposed on it is the transfer sheet onto which the image is to be transferred. That is, according to the image transfer method according to the preceding invention, as shown in the drawing, the up and down relationship between the transfer sheet and the image receiving sheet is in the reversal relationship to the conventional one. In the conventional image transfer method (FIG. 10), the image receiving sheet R on which the image is formed, is superimposed on the transfer sheet onto which the image is to be transferred, however, herein, in reverse to it, it is a feature that the transfer sheet P is superimposed on the image receiving sheet R. Like this, initially, when the sheets are inserted into the image transfer apparatus in the condition in which the image receiving sheet R is positioned on the insertion platform 2, and the transfer sheet P is superimposed on it, because the transfer sheet which easily includes the humidity is placed in upper portion of them, even when the sheets are heated by the heat rollers 41 and 42, the water content included in the transfer sheet is converted into the water vapor and flies upward, thereby, the wrinkle and indent are not generated.
In this case, in the positional relationship of the image receiving sheet and the transfer sheet, it is preferable that the transfer sheet P is inserted in front of the image receiving sheet R by more than L1 (L1=21 mm). According to this, only the transfer sheet P is passed before, and next the superimposed portion with the image receiving sheet R is passed, and the sheet conveyance failure (ordinary, called [jam]) is reduced.
According to this preceding invention, when the transfer sheet P and the image receiving sheet R are superimposed at the time of insertion, although the positioning of both sheets is improved a little by using a mark, the correct positioning is conducted by looking through the transfer sheet and aligning it to the edge of the lower side image receiving sheet, and because it takes a long period of time, and requires the techniques, the positioning is still inconvenient.
In order to solve the problems, according to the invention of the first aspect, in the insertion platform to send the superimposed sheets in which the image receiving sheet on which the image is formed, and the transfer sheet onto which the image is to be transferred, are superimposed, to the heat roller pair to heat and press the sheets in the image transfer apparatus, the insertion platform is characterized in that a part or the whole of it is structured by a member having a function to transmit the light from the lower side.
Further, according to the invention of the second aspect, the light transmission function member is characterized in that it is any one of a transparent portion, translucent portion, light diffusion portion, or opening portion.
Further, according to the invention of the third aspect, the insertion platform for the image transfer apparatus is characterized in that the light source is provided on the lower side.
Further, according to the invention of the fourth aspect, it is characterized in that a light accumulation fluorescent substance is coated on the light transmission function member and/or its periphery.
Further, according to the invention of the fifth aspect, it is characterized in that the external light lighting hole is provided on the lower side.
According to the structure described as above, when the transfer sheet P and the image receiving sheet R are superimposed at the time of insertion, because, by using such the insertion platform, both sheets are viewed being made transparent by the light from the lower side, the superimposition of match-marks of (+) mark of both sheets can be correctly conducted, accordingly, even when the operator is not a skilled person, the positioning can be correctly conducted without spending a long period of time.
Further, according to the invention of the sixth aspect, it is characterized in that the insertion platform is provided with a cutout having the length in which the operator can continuously have the superimposed sheets until the leading edge of both sheets in the superimposed condition is nipped.
According to the structure as described above, the operator can securely insert the correctly positioned superimposed sheets of the transfer sheet P and the image receiving sheet R from the insertion platform into the device, while he having the superimposed sheets.
According to the invention of the seventh aspect, it is characterized in that the insertion platform for the image transfer apparatus of any one of the first aspect to the fifth aspect, and the heat roller pair to heat and press the superimposed sheets entering from the insertion platform, are provided.
According to the structure as described above, because the image transfer apparatus has the insertion platform as described above, the image transfer apparatus can transfer the correctly positioned transfer sheet P and the image receiving sheet R, and can transfer the fine image having no image slippage and no indent.